【正文】 y anim al s and prodeced mi lk to feed them . Finnal y about 2. 6 mil li on years ago som e sm al l cel ver anim al s, now wi th hands and feet, apeared and spread al over the earth. Thus they have, i n thei r turn, be e the m ost i mportant anim als on the pl a. But they no they l ooki ng after the earth very wel l. They are putti ng too much carbon di oxi de i nto the atm osphere, whi ch prevenrs heat from escapi ng from the earth i nto space. As a result of thi s, m any sci enti sts beli eve the earth m ay b e too hot to l i ve on. So whether li fe wil l conti nue on the earth for mi l i ons of years to e wil l depend on whether thi s probl em can be sol ved. A vi si t to the m oon Last m onth I was l ucky engough to have a chance to make a tri p i nto space wi th m y fri end Li Yanpi ng, an astronom er. We vi si ted the m oon i n our spaceshi p! Before we l eave, Li Yanpi ng expl ai ned to m e that the forece of the gravi ty woul d change three ti mes on our journey and that the fi rst change woul d be the m ost powerful . Then we were off. As the rocket rose i nto the ai r, we were pushed back i nto our seats because we were tryi ng to escape the pul l of the earth’s gravi ty. It was so hard that we coul d not say anythi ng to each other. Gradual y the wei ght l esened and I was abl e to tal k to hi m. “ Why i s the spaceshi p not fal i ng back to the earth? O n the earth i f I fal from a tree I wi l fal to ground.” I asked. “ We are to far from the earth now to feel its pul , “ he expl ai ned, “ so we feel as i f there i s no gravi ty at al . When we get cl oser to the m oon, we shal feel its gravity pul i ng us, but i t wi l not be as strong a pul l as the earth’s. “ I cheered up imm edi atel y and floated wei ghtl essl y around in our spaceship cabi n watchi ng the earth bee sm al l er and the m on l arger. When we got there, I wanted to expl ore imm ediately. “ Com e on, ” I sai d. “ If you are right, m y m ass wil l be l es than on the earth because the m oon i s sm al l er and I wi l be abl e to m ove more freely. I mi ght even grow tal er i f I stay here l ong enough. I shal l certai nl y wei gh l ess!” I l aughed and clim bed down the steps from the spaceshi p. But when I tri ed to step forward, I found I was carri ed twi ce as far as on the earth and fel l over. “ O h dear, ” I cri ed, “ wal ki ng does need a bi t of practi ce now that gravity has changed.” After a whil e I got the hang of i t and we began to enjoy ourselves. Leavi ng the moon’s gravity was not as pai nful as l eavi ng the earth’s. But returni ng to the earth was very fri ghteni ng. We watched, am azed as fire broke out on the outsi de of the spaceshi p as the earth’s gravi ty i ncreased. Agai n we were pushed back hard i nto our seats as we cam e back to l and. “ That was very exhausti ng but very exci ting too,” I sai d. “N ow I know m uch m ore about gravi ty! Do you thi nk we coul d bi sit som e stars next tim e?” “O f course, ” he smi l ed, “ whi ch star woul d you li ke to go to?” Caught by a bl ack hol e The spaceshi p warned Li Yanpi ng and m e to be ready as we were aproaching the “bl ack hole”. We coul d see some fai nt l ights around what looked l ike an empty space. Li Yanping sai d, “ That empty hol e i s li ke a m outh always needing to be fed. Those li ghts are thins that are bei ng pul ed into ti me by the gravi ty of the hol e. ” We watched wi th interest and amazement at the lights whi ch seemed to be going fai nter and fainter round the edge of the bl ack hole. Just then the l ights on our spaceship went our the and the puter stoped worki ng. What was hapeni ng? I tried to turn the spaceship away from the hol e but i t would not move. Would it eat us too? Suddenly the spaceship jumped and began to move round the edge of trhe hole too. The gravity of the “bl ack the bil l, si r, pl ease fet i t. H enry: Fet i t? Wel … thank you very m uch. That39。t thank the gentl em en properl y. May I do it for you? H enry: Let m e see you try. (Porti a wal ks over to Roderi ck and gives him a hug. Then she sits i n Ol i ver’s l ap, puts her arm s around hi s nevk and ki sses him on the cheek. Oli ver begi ns l aughi ng.) Porti a: Papa, he says he doesn39。 ㈢項(xiàng)目建設(shè)單位 ****農(nóng)業(yè)種植有限公司。s very ni ce of you. O wner: O h, i t’s for US to thank you, si r and I do, si r, from the botom of my heart. (the owner, hostes and wai ter al bow as H enry l eaves) Act Ⅱ , Scene 4 N arrator: at the end of the m onth, H enry was very ri ch and di dn39。t want anythi ng el se from you. H enry: (shocked) My dear, i s that your papa? Porti a: H e’s m y step father, and the dearest one that ever was. H enry: O h, m y dearest dear si r, I regret what I sai d. You have got a job open that I want. Ol iver: Nam e it. Henry: Soninl aw. O li ver: Wel , wel , wel l! But you’ve never had such a job before. H ow can i t be sure you can do i t successful y? H enry: Try m e… oh, do, I beg of you! Gi ve m e 30 or 40 years , and … O li ver: O h, wel, al l ri ght. N arrator: Are Porti a and H enry happy? There are not enough word i n the bi ggest di cti onary to descri be i t. Di d the peopl e of London have a good tim e wi th thi s bit of news? Yes. Portia’s stepfather took that bank note back to the Bank of Engl and and cashed it. The bank note was then usel es for m oney but was hi s weddi ng gift to the young coupl e. Yes, the bank note was worth m il li ons of dol ars, but not worth on tenthe as m uch as how H enry felt about Porti a . Uni t 4 H ow li fe began on the earth No one knows exactl y how the earth began, as i t happened so l ong ago. However, accordi ng to a wi del y accepted theory, the uni verse began wi th a “ Bi g Bang “ that threw m atter in al l directi ons. After that, atom s began to form and bing to create stars and other bodies. For several bil li on years after the “ Bi g Bang “, the earth was sti l just a cl oud of dust. What i t was